1. Field of the Invention
This invention relates to an improved method for preparation of zeolites ZSM-4 and ZSM-5 which have uniform pores and which are greater than 40% crystalline. The improvement resides in forming a reaction mixture in each instance having a specific critical compositional range as follows:
______________________________________ ZSM-4 ZSM-5 ______________________________________ Na.sub.2 O+R.sub.2 O/Al.sub.2 O.sub.3 0.60-1.75 0.15-0.85 Na.sub.2 O+R.sub.2 O/SiO.sub.2 0.24-0.65 0.04-0.18 Na.sub.2 O/Na.sub.2 O+R.sub.2 O 0.75-0.92 0.30-0.85 SiO.sub.2 /Al.sub.2 O.sub.3 1.8-4.3 1.8-6.0 H.sub.2 O/R.sub.2 O+Na.sub.2 O 9-60 35-360 ______________________________________
wherein R is a tetramethylammonium cation for ZSM-4 preparation and a tetraalkylammonium cation, the alkyl groups of which preferably contain 2-5 carbon atoms, for ZSM-5 preparation, and wherein at least about 70 weight percent of the Al.sub.2 O.sub.3 is provided by an alumina-containing clay, e.g. kaolin, being added to the reaction mixture.